Abstract The adsorption of NO and its coupling to yield N 2O 2 on Rh(100), Pd(100) and Pt(100) surfaces is analyzed using extended Hückel calculations. It appears that the Blyholder model is a valid description of the chemisorption of NO on Rh(100). There is substantial weakening of the NO bond on this surface. However, in the case of Pd(100) and Pt(100), the NO overlap population increases upon chemisorption. For some of the geometries studied, the results indicate that for rhodium surfaces the coupled product has significant NN double bond character, best described by the 6π electron system, hyponitrite. For rhodium surfaces the dimerization of chemisorbed NO seems to be a viable initial step in the NO reduction mechanism.